During the first half of May, Cornwall Wildlife Trust had received many reports from members of the public who had found huge numbers of alien-looking blue creatures stranded on Cornwall’s beaches including Lansallos beach near Polperro, Port Gaverne and Port Quin.

At first glance resembling an oval jellyfish, and a deep, vivid blue with concentric circles like a fingerprint and a fin-like ‘sail’, these wonders of the ocean are known by the scientific name Velella velella, or the more common name, ‘by-the-wind-sailor’.

Some of the creatures were no bigger than a 50p coin, while others were more substantial, up to 10cm long.

Matt Slater, Marine Conservation Officer at Cornwall Wildlife Trust, explains what Velella velella actually are: “These creatures are hydrozoans – a colony of tiny individual animals called hydroids. They are similar to the Portuguese man o’ war, rather than jellyfish. They float on ocean currents, and the sail on top allows them to catch the wind like a sailing boat and travel long distances effortlessly, using their stinging tentacles to catch small marine organisms as they go. The colony are connected by canals that enable the individuals to share the food.”

“Fortunately, the stings are not powerful enough to harm humans or dogs, although it is not advisable to touch them and then touch your face and eyes, as they may cause skin irritation. Dogs love eating them – they have a strong smell of the ocean – but I don’t think they are good for them.”

Asked why they have appeared on Cornwall’s beaches in such numbers this month, Matt replied; “As their common name suggests, by-the-wind-sailor are at the mercy of the prevailing winds. They live their entire lives in the open ocean, and it’s bad news for them if they ever meet land. If there are extended periods of onshore breezes, they can be blown ashore from further out to sea. We have had really strong north and north-west winds for well over a week, which is probably why they have been coming ashore in such numbers. Sadly, once they are onshore, they die, and it’s futile trying to save them if the winds are onshore. However, new floating colonies will already be forming out in the ocean.”